1. Field of the Invention
This invention relates to crushing apparatus and, more particularly, relates to a crushing apparatus capable of agitating to crush a material which has been introduced into a crushing tank to obtain a product in the form of a fine powder.
2. Description of the Related Art
In general, there is a type of crushing apparatus in which a material is introduced into a crushing tank and an agitator is then rotated to crush the material into pulverized particles in the form of a fine powder. Some of this type contain media in the crushing tank so that the material introduced into the crushing tank is to be crushed while it is agitated together with the media.
Such media-agitation type crushing apparatus crushes up the material by means of shearing force and impact force which are generated at the time of agitation, where its crushing ability is several tens of times greater than that of a ball mill.
However, while having a high crushing ability, the crushing efficiency of the crushing apparatus as described is relatively low.
Specifically, when the material is crushed up into pulverized particles in the form of a fine powder especially in a dry crushing apparatus, the pulverized particles in the form of a fine powder may be aggregated within the crushing tank to equilibrate the crushing process.
The pulverized particles in the form of a fine powder have a strong tendency to aggregate. As a result, the material once crushed into the form of a fine powder is aggregated to be increased in particle size again, even though it is in the process of agitation/crushing by means of the media.
Accordingly, when crushing action and aggregating action are repeated within the crushing tank, the crushing process is brought into an equilibrium to halt the progress of crushing even if a larger amount of energy for crushing is supplied. The obtainable particle size of the pulverized particles as a product is limited, resulting in a lower crushing efficiency.
Further, some crushing apparatus have a built-in classifier for improving accuracy in the fineness of the product.
A classifier having a high-speed rotor is usually used as the classifier incorporated into such crushing apparatus. Since the material crushed into the form of a fine powder tends to cause clogging at the rotating portion of the rotor, an obstacle on the rotation of the rotor may result to lower the classifying efficiency.
Further, re-aggregation of the material tends to occur to cause a lowered classifying efficiency. In addition, thus aggregated fine powder is returned to the interior of the crushing tank, resulting in a problem that the crushing efficiency may be reduced.